1. Field of the Invention
The invention relates to a detecting device and a detecting method. Particularly, the invention relates to a detecting device for detecting a rotation speed of a motor of a color wheel and a detecting method thereof.
2. Description of Related Art
A reason why a projection apparatus can provide color images is because that a lighting system of the projection apparatus can sequentially provide a red, a green and a blue illumination beams to a light valve in the projection apparatus, so that the projection apparatus can sequentially project red, green and blue images on a screen. When the red, green and blue images are quickly cycled in a sequence, due to a visual staying effect, the red, green and blue images are mixed to form a color image, and this is why the projection apparatus can provide the color images.
Generally, the lighting system may transmit the illumination beams to pass through a rotating color wheel, and the color wheel is formed by a red fan-shaped filter, a green fan-shaped filter and a blue fan-shaped filter, so that after the illumination beams pass through the color filters of the rotating color wheel, a red beam, a green beam and a blue beam are sequentially formed. Moreover, the lighting system detects a rotation speed of the color wheel through a conventional detecting device to determine whether the color wheel normal operates, wherein the conventional detecting device can shield a light or let the light to pass through via a mark or a special structure on the color wheel, so as to detect the rotation speed of the color wheel and a start position of the color wheel. However, the conventional detecting device can be influenced by dust and other light sources to obtain an error result and a light intensity of the light source and a sensing distance have to be considered.
Taiwan Patent No. I269115 discloses a base locating device and a base locating method of a color wheel, in which a position of the color wheel is determined according to a through hole on the color wheel, so as to determine a switch time of signal modulation of a received one-way signal relative to various colors of the color wheel. Taiwan Patent No. I294717 discloses a motor driver, a motor controller and a method for controlling an electric motor, in which a position detecting circuit outputs a position signal corresponding to a position of a motor rotor, and a current command generating circuit and a space vector modulation control circuit select one of a plurality of stator coils according to the position signal, and control a current magnitude of the stator coil, so as to control the electric motor.